This invention relates to a multichannel type magnetic head utilizing the Hall effect for magnetic/electric conversion, and a specific method for producing this magnetic head.
There are known two types of magnetic heads for detecting information recroded on magnetic recording media. One includes a high-permeability core with a winding wound thereon to form a magnetic flux circuit, while the other is composed of a semiconductor Hall element inserted in a front or back gap in the magnetic flux circuit. In the winding-type magnetic head, a reproduced output is proportional to the time-based changing rate d.phi./dt of detected magnetic flux .phi.. Therefore, the reproduced output is reduced as the frequency of the detected magnetic flux .phi. is lowered. Accordingly, it is impossible to detect magnetic flux subject to no time-based change. Since the winding-type head requires a winding space, the track intervals between channels cannot fully be narrowed in forming a multichannel-type head.
In the Hall-element type magnetic head, on the other hand, the reproduced output is proportional to the magnitude of the detected magnetic flux itself. Accordingly, if the frequency-based change of the magnitude of the magnetic flux flowing through the magnetic flux circuit is negligible, the substantial output level will hardly exhibit any dependence upon frequency. This means that a flat frequency characteristic can be obtained over a considerably wide frequency range from the DC region to the high-frequency region. Furthermore, the space occupied by the Hall element may be made extremely small so that the track intervals between channels may be sufficiently narrowed for constituting the multichannel head. Thus, the magnetized surface of the tape may be utilized efficiently, and the track density may be increased.
A multichannel head utilizing these characteristics of the Hall element is disclosed in Japanese Patent Disclosure No. 44,814/75. In the magnetic head disclosed in this application, independent Hall elements are used for separate channels in order to eliminate crosstalk between the channels. A current supply line and a signal output line are disposed for each of these Hall elements. Consequently, the number of external terminals of the head becomes too large to form a multichannel head with many channels. Furthermore, as may be seen from this specification, when a semiconductor Hall element of, for example, indium-antimonide (InSb) is used as the Hall element, it becomes difficult to obtain a high S/N ratio (signal to noise ratio) and good resolution (excellent high frequency response) simultaneously.
When disposing the Hall element at the front gap side, the gap width for detection of signals is greater than the thickness of the Hall element. It thus becomes necessary to use a thinner Hall element for narrowing the front gap to obtain a higher resolution. In a general Hall element using a semiconductor polycrystalline thin film, a typical example of which is indium-antimonide, the thinner the element becomes, the more the element is affected by the boundary regions of the polycrystals and the greater becomes the current noise. Thus, with the magnetic head which uses a thin semiconductor Hall element for obtaining higher resolution, more current noise tends to be generated and it is difficult to obtain a high S/N ratio.
This problem also applies to the case where the semiconductor Hall element is disposed in the back gap. In this case, although the thickness of the Hall element does not directly affect the reproduction resolution, it indirectly affects the reproduction resolution from the viewpoint of reproduction efficiency. However, the narrower the front gap, the lower the reluctance of the front gap and hence the reproduction efficiency will be deteriorated. Such effect is produced because most of the detected magnetic flux is shunted at the front gap section with the low reluctance to reduce the magnitude of the magnetic flux transmitted to the Hall element in the back gap. When narrowing the front gap to improve the frequency characteristic (resolution) of the magnetic head as a whole, therefore, it is essential to provide an efficient magnetic flux circuit. Namely, the reluctance of the magnetic flux circuit including the back gap with the Hall element inserted therein needs to be low enough.
The most effective method for lowering the reluctance of the magnetic flux circuit is to narrow the back gap. The permeability of the semiconductor Hall element is much lower than that of the high-permeability ferromagnetic substance forming the magnetic flux circuit. Accordingly, the reluctance of the magnetic flux circuit can greatly be lowered by reducing the width of the back gap even by a very small margin in microns. This implies that the thickness of the Hall element must be reduced. Then, similar problems arise as in the case wherein the Hall element is disposed in the front gap. Namely, when the front gap is narrowed for obtaining a higher resolution and the back gap is narrowed to compensate for the resultant degradation in the reproduction efficiency, the Hall element must be made thinner and the current noise increases.
The present invention has been made to overcome these problems of the prior art and has for its object to provide a multichannel magnetic head and a manufacturing method therefor, wherein the number of external terminals is smaller, and the resolution, S/N ratio and track density are improved.